Cross-Reference to Related Application
This application is related to U.S. patent application Ser. No. 581,465, filed of even date, which concerns a method of separating primary amine from tertiary amines using a non-polar hydrocarbon alone or in conjunction with a polyhydroxylic compound.
1. Field of the Invention
The invention relates to amine liquid-liquid extration separation methods and more particularly relates to methods for the separation of primary amines from tertiary amines which have close boiling points, by means of a non-polar hydrocarbon solvent and water.
2. Description of Other Relevant Methods in the Field
Bis-(2-aminoethyl)ether (BAEE) and N-(2-methoxyethyl)morpholine (MEM) are co-products in the production of morpholine when diethylene glycol and ammonia are used as the reactor feed. These two co-products are very difficult to separate by conventional distillation because of their close boiling points. It would be advantageous to separate these two compounds because BAEE can be methylated to form .beta.-(N,N-dimethylamino)alkyl ethers which are useful as catalysts in polyurethane isocyanate reactions according to U.S. Pat. No. 3,330,782, incorporated by reference herein.
No method has been found for the separation of these two compounds. However, amines have been separated from other compounds according to some of the following techniques.
For example, U.S. Pat. No. 3,033,864 discloses the purification of pyrazines and piperazines by azeotropic distillation. In that patent, the goal was to remove unreacted alkanolamines by using codistillation agents comprising aliphatic hydrocarbons, aromatic hydrocarbons and nuclear chlorinated aromatic hydrocarbons having normal boiling points between about 130.degree. and 200.degree. C. Representative examples given were octane and higher aliphatic hydrocarbons, petroleum fraction mixtures, ethyl cyclohexane, ethylbenzene, the xylenes, diethylbenzene, ethyl toluene, cumene and chlorobenzene.
A process for recovering piperazine from a mixture with triethylenediamine is described in U.S. Pat. No. 3,105,019. The inventors therein found that aliphatic hydrocarbons and especially saturated aliphatic hydrocarbons would be suitable azeotropic agents for the piperazine-triethylenediamine split if the boiling points were in the range from 110.degree. C. to about 200.degree. C., with particularly good results being obtained if the boiling point is within the range from about 140.degree. C. to about 160.degree. C. Specific compounds mentioned and tried were 3-methylheptane, 2-ethyl hexene, 1,2-dimethyl cyclohexane, meta-xylene, nonane, styrene, mesitylene, kerosene and 1-methyl naphthalene.
A method for recovering the major by-products from piperazine reaction residue is presented in U.S. Pat. No. 3,331,756. It was taught therein that hydrocarbons immiscible with diethylenetriamine and boiling within the range of about 175.degree. to about 250.degree. C. would be suitable entrainers for use in the separation of diethylenetriamine and aminoethylpiperazine. Two azeotropic agents mentioned were tetrapropylene and n-dodecane, with tetrapropylene being preferred because it gave a cleaner separation.
Russian Pat. No. 472,122 teaches that diethylenetriamine and aminoethylpiperazine may be separated from reaction mixtures (especially those from the synthesis of a diamine and piperazine) by means of azeotropic rectification using a hydrocarbon mixture boiling at 160.degree. to 174.degree. C. yielding an azeotrope with DETA. The inventors found that the fractionation is simplier with n-decane than with dodecane or tetrapropylene.
The separation of an alkylene open chain polyamine from a piperazine compound may be accomplished by complexing the polyamine with a salt selected from the group consisting of sulfates and chlorides of copper, nickel, cobalt and zinc, according to the invention disclosed in U.S. Pat. No. 3,038,904. The complex compounds are extracted with substances such as chloroform or are allowed to precipitate out. U.S. Pat. No. 3,400,129 reveals that 2-methyl triethylenediamine can be purified in a process which incorporates a two-solvent extraction step. One of the solvents is water and the other is an organic solvent for pyrazines, such as hexene, octene, nonene, benzene, toluene, xylenes, ethyl benzene, propyl benzene, n-hexane, n-heptane, isooctane, n-nonane, methylnonane, chlorobenzene, chlorotoluenes, diethylether, furan and alkylbenzonitriles. The method includes an azeotropic distillation step where 2-methylpiperazine is distilled and a step where the purified 2-methyl triethylenediamine is recovered.
Further, in Advances in Chemistry Series No. 116: Azeotropic Data III, 1973, L. H. Horsley lists a number of binary azeotropic systems.